The invention relates to a crucible of pure silica glass (transparent, translucent, or opaque fused, vitreous silica) and to a method of making same, especially for use in the production of monocrystals used in making semiconductor elements.
German Pat. No. 962,868 discloses crucibles for the production of monocrystals by the Czochralski method. These monocrystals are used in making semiconductor elements. The crucibles consist of quartz (transparent fused silica made from rock crystal) and are provided on their interior with a coating of pure silicon dioxide obtained by the rectification of silicon tetrachloride followed by hydrolysis. These crucibles have proven practical, but the making of such a crucible requires a great expenditure of force and energy.
Crucibles of pure silica glass for use in making monocrystals, especially silicon monocrystals for the semiconductor art, have hitherto been made by heating one end of a pure silica glass tube and, while the glass is in the plastic state, forming the head of the crucible from the marginal portions. The crucible is given its precise shape by blowing it in a graphite mold. This process has the disadvantage that, in the case of crucibles of relatively large diameter very much energy is required in order to form the head of the crucible from the wall of the tube. Since the tube circumference increases linearly with the diameter but its end area increases as the square thereof, the prior art process becomes all the more uneconomical as the diameter of the crucible increases.